How to think in a OOP way?

How to think in a OOP way?

i am creating a test site which is kind of like a to do list and which
keeps track of your progress. the user will enter an item with its time
limit and the site should keep track of all the information.
so i created 4 tables:
1. for the main title of my list
2. for the items in each title
3. amount of progress i made in each item
4. time i allotted to each item.
now, i am new to php and mysql so is this the right way to tackle this
problem? how many classes should i create to get all these information in
a easy and understandable way.
Thank You